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Only steel that is high in carbon can be hardened and tempered. If a metal does not contain the necessary quantity of carbon, then its crystalline structure cannot be broken, and therefore the physical makeup of the steel cannot be altered. Frequently, the term "hardening" is associated with tempered steel. Both processes are used hand in hand ...
Martensitic transformation, more commonly known as quenching and tempering, is a hardening mechanism specific for steel. The steel must be heated to a temperature where the iron phase changes from ferrite into austenite, i.e. changes crystal structure from BCC (body-centered cubic) to FCC (face-centered cubic). In austenitic form, steel can ...
Diagram of a cross section of a katana, showing the typical arrangement of the harder and softer zones. Differential hardening (also called differential quenching, selective quenching, selective hardening, or local hardening) is most commonly used in bladesmithing to increase the toughness of a blade while keeping very high hardness and strength at the edge.
To harden by quenching, a metal (usually steel or cast iron) must be heated above the upper critical temperature (Steel: above 815~900 degrees Celsius [23]) and then quickly cooled. Depending on the alloy and other considerations (such as concern for maximum hardness vs. cracking and distortion), cooling may be done with forced air or other ...
Case-hardening or carburization is the process of introducing carbon to the surface of a low-carbon iron, or more commonly a low-carbon steel object, in order to harden the surface. Iron which has a carbon content greater than ~0.02% is known as steel .
When a hot steel work-piece is quenched, the area in contact with the water immediately cools and its temperature equilibrates with the quenching medium.The inner depths of the material however, do not cool so rapidly, and in work-pieces that are large, the cooling rate may be slow enough to allow the austenite to transform fully into a structure other than martensite or bainite.
The steel is then quenched so that the austenite is transformed into martensite, and the ferrite remains on cooling. The steel is then subjected to a temper cycle to allow some level of marten-site decomposition. By controlling the amount of martensite in the steel, as well as the degree of temper, the strength level can be controlled.
Precipitation hardening, also called age hardening or particle hardening, is a heat treatment technique used to increase the yield strength of malleable materials, including most structural alloys of aluminium, magnesium, nickel, titanium, and some steels, stainless steels, and duplex stainless steel.